The primary objective of this study is a Phase I study to assess the safety and efficacy of recombinant factor IX (rhFIX) administrated by intravenous infusion in patients with severe hemophilia B. Secondary objectives are: (1)to estimate the pharmacokinetic parameters, including recovery and half-life, of rhFIX administered as an intravenous infusion during the first segment of the study; (2)to evaluate the pharmacokinetic parameters, including half-life and recovery of rhFIX and Mononine during the first segment of the study.